Brushless rotary electrical machines such as motors, generators and alternators have typically suffered from one or more of the following deficiencies, low power capability, heavy weight, low efficiency, complex and costly construction, cogging, and required use of expensive and complex cooperating electronics. One prior art electromotive device that functions as a brushless motor or generator does achieve a very high ratio of power capability to weight through use of many rare earth magnets arranged on a substantially hollow rotor that cooperate with numerous windings wound around flux conducting bars. Unfortunately, this construction is complicated and the use of many rare earth magnets and low loss magnetic conducting bars is expensive. Besides the expense of the electrical machine itself the associated electronics to drive the electrical machine are also expensive. Because the flux in the machine is generated solely by permanent magnets, the induced voltages in the armature windings will be directly proportional to the rotor speed. Complex high frequency switching electronics is usually necessary with such permanent magnet machines to regulate power to and from the electrical machine whether used as a motor or generator. These electronics can be prohibitively expensive for use of the electrical machine in many applications and the life of these electronics can be limiting.
Another type of brushless electrical machine that can overcome the need for costly electronics to provide power regulation is an inductor alternator. The magnetic flux in the electrical machine is provided by a stationary field coil that generates flux through application of an electric current. Proper design of the electrical machine can require only a small field current to generate a large flux by using many turns in the field coil. The power to and from the electrical machine can be controlled simply by varying the current to the field coil. When used as a generator, increasing the field coil current increases the voltage induced in the armature windings for a given rotor speed. When the electrical machine is used as a motor, a synchronous inverter energizes the armature windings to cause the rotor to rotate. Varying the current to the field coil can control the speed and torque. Although such electrical machines can reduce the cost of associated electronics for operation, they are heavy and have provided only a very low ratio of power capability to weight.